Normalize Motherduck Jumbo to jumbo in pg_duckdb-motherduck

motherduck/ uses lowercase tier names ("Motherduck: jumbo",
"Motherduck: mega", "Motherduck: standard"); pg_duckdb-motherduck/
had three files with "Motherduck: Jumbo" (capital J). Lower-case the
J so the dashboard groups all jumbo-tier runs under one machine.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: alexey-milovidov

pg_duckdb-motherduck/results/20240307/motherduck.json

@@ -1,7 +1,7 @@
 {
     "system": "pg_duckdb (MotherDuck enabled)",
     "date": "2024-03-07",
-    "machine": "Motherduck: Jumbo",
+    "machine": "Motherduck: jumbo",
     "cluster_size": "serverless",
     "proprietary": "yes",
     "hardware": "cpu",

pg_duckdb-motherduck/results/20241123/motherduck.json

@@ -1,7 +1,7 @@
 {
     "system": "pg_duckdb (MotherDuck enabled)",
     "date": "2024-11-23",
-    "machine": "Motherduck: Jumbo",
+    "machine": "Motherduck: jumbo",
     "cluster_size": "serverless",
     "proprietary": "yes",
     "hardware": "cpu",

pg_duckdb-motherduck/results/20250904/motherduck.json

@@ -1,7 +1,7 @@
 {
     "system": "pg_duckdb (MotherDuck enabled)",
     "date": "2025-09-04",
-    "machine": "Motherduck: Jumbo",
+    "machine": "Motherduck: jumbo",
     "cluster_size": "serverless",
     "proprietary": "yes",
     "hardware": "cpu",